1. Field of the Invention
The present invention relates generally to power supplies and, more particularly, to thermoelectric power supplies.
2. Related Art
Medical devices which are partially or completely implanted in a patient often require power to perform various therapeutic or diagnostic operations. Such power-consuming medical devices, commonly referred to as active implantable medical devices, or AIMDs, obtain the requisite power from a variety of power sources. Conventional power sources include, for example, implanted non-rechargeable and rechargeable batteries, an external energy storage device operatively connected to the implanted device via a percutaneous lead or a transcutaneous transfer system, electrochemical elements, biofuel cells, nuclear batteries and devices for direct conversion of the mechanical energy of motion into electric power by means of mechanical-electrical converter principles, mechanical micro-variation systems and the like. Such conventional approaches have a variety of associated drawbacks as described in U.S. Pat. Nos. 6,131,581, 6,470,212 and 6,640,137, which are hereby incorporated by reference herein in their entireties.
One power source of particular relevancy to the present invention is a thermoelectric device. Thermoelectric devices are very small, very light and completely silent solid state devices that can operate as a heat pump or as an electrical power generator with no moving parts. Thermoelectric devices such as Peltier effect-based thermoelectric power generators and Seebeck effect-based thermoelectric energy converters, act to directly convert the thermal energy of the body into electrical energy so as to provide an AIMD with electrical energy. U.S. Pat. No. 6,131,581, which is hereby incorporated by reference herein, shows a Seebeck effect-based thermoelectric device. This device functions by effectively harnessing the temperature difference between the core temperature of the body and the surface temperature of the body at the implantation site, or by harnessing temperature gradients within the body. This temperature difference, as a thermodynamic form of energy, is converted directly into electrical energy by the thermoelectric device. The Seebeck effect is achieved, for example, by the structural pairing of different metals which are spaced far apart in thermoelectric series. Even more efficient use of the Seebeck effect may be attained by the constructive connection of specially doped semiconductor materials as discussed in U.S. Pat. No. 6,131,581.